This invention relates to cutting tool holders. More particularly, the invention relates to holders of the type having a rotary automatic opening and closing collet.
Applications, such as sharpening of drill bits, often require that the drill bit be continuously rotated during the sharpening process so as to generate the proper cutting surface shape. The sharpening process is normally carried out by bringing the tool to be sharpened into contact with a grinding wheel while simultaneously rotating the tool. My co-pending U.S. application Ser. No. 588760, filed Mar. 13, 1984, discloses a semi-automatic grinding machine for sharpening these types of cutting tools. The tools to be sharpened are normally held in collets of the type having longitudinally elongated jaws that are biased normally open and are caused to engage and frictionally hold the tool by a surrounding spindle that collapses the jaws around the tool.
Additionally, automatic opening and closing collet type holders have been designed, however, while these holders are effective, it would be desirable to provide for a continuously rotating tool holder that includes protection from damage due to lock up should either the spindle or collet become jammed during operation.